1. Field of the Invention
The present invention relates to voltage controlled switches and more particularly pertains to a voltage controlled latching relay that switches between direct current voltage sources, such as batteries, supplying power to a common load, with virtually no interruption in load current being experienced during the switch.
2. Description of the Prior Art
One of the more critical problems confronting developers of voltage controlled switches, which are designed to switch from one direct current voltage source to another, is the momentary loss of load current being delivered to the load as a result of the switchover between power sources. One approach for overcoming this problem has been to provide a mechanical interlock for manually exchanging power sources supplying a common load. In this connection, two power sources are first connected in parallel, and then the primary power source may be removed safely with no load voltage interruption. Of course, this method of switching between power sources to prevent a load interruption requires that an operator be aware of when the principal power source has reached an unacceptable level of power output and further, it requires the physical presence of the operator at the time the switchover occurs.
As to power switchover relays that are automatic in operation, i.e., which require no manual operation but which respond automatically to a power output drop in the principal power source, the prior art devices typically utilize parallelly arranged power sources which either break the circuit during a power switchover, so as to allow a momentary drop in load current, or which maintain the separate power sources in parallel communication at all times, but even though a switchover may occur, a drop in load current will still be experienced due to the fact that the secondary power source will supply charging current into the primary power source. As such, both of these prior art automatic switching methods still permit some drop in load current during a switchover from a first to a second direct current power source.
Accordingly, it can be appreciated that there still exists a need for automatic power switchover devices which permit no drop in load current during such a switchover, and the present invention substantially fulfills this need.